This application claims the benefit of Korean Patent Application No. 2002-37606 filed on Jun. 29, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a microwave oven, and a method of controlling the same, which controls the level of output power according to cooking times to prevent overheating of the microwave oven.
2. Description of the Related Art
Generally, microwave ovens are devices which heat/cook foods using microwaves. FIG. 1 shows a conventional microwave oven having a body 1 which defines an external shape of the microwave oven, a cooking chamber 5 which is formed in a left side of the body 1 and accommodates food therein, and a key input unit 9 which is installed in a right side of the body 1 and is used to input information including a cooking menu item, a cooking time, an output power level, and a cooking start instruction. A door 3 which opens/closes the cooking chamber 5 is attached to a portion of the body 1 using a hinge.
The conventional microwave oven having the above-described construction is provided with a function which controls the level of its output power. In the conventional microwave oven, the output power level is increased/decreased by controlling a switching-on time, for which power is supplied to a high voltage transformer, and a switching-off time, for which the supply of power to the high voltage transformer is intercepted. That is, the output power level can be decreased by shortening the switching-on time in a predetermined period for a power relay disposed between a power terminal and the high voltage transformer. Accordingly, the switching-off time is relatively lengthened. In contrast, the output power level can be increased by lengthening the switching-on time for the power relay. In response, the switching-off time is relatively shortened.
In the conventional microwave oven, where a magnetron is continuously driven for an extended time, by supplying power to the high voltage transformer, overheating is generated in various electrical parts including the high voltage transformer. Accordingly, the output power level is controlled according to cooking times. For example, to prevent overheating in the conventional microwave oven, a cooking time is counted during a cooking operation, and the power relay is controlled to decrease the output power level where the counted cooking time reaches a preset time. The remaining cooking operation is performed while the decreased output power level is maintained.
However, the conventional microwave oven uniformly counts a cooking time regardless of a practical aspect of the cooking operation during the performance of the cooking operation by the driving of the magnetron, and controls the output power level on the basis of the counted cooking time. Consequently, a cooking time is increased even where a user manipulates a pause key so as to temporarily stop the cooking operation, and in response, a control unit turns off the power relay according to the operation of the pause key. Where the increased cooking time reaches a predetermined time, the control unit decreases the output power level by shortening a switching-on time of the power relay so as to prevent overheating, and performs the remaining cooking operation using the decreased output power level.
Due to the above-mentioned operations, the output power level set by the user or automatically set by a control program cannot be maintained, and the remaining cooking is carried out using the decreased output power level. As such, the conventional microwave oven cannot perform an optimal cooking operation with respect to a corresponding cooking menu item. Therefore, a cooking performance is decreased, and in most cases, the entire cooking time is increased.
That is, during an operation in which electrical parts, including the high voltage transformer, are cooled by external air, like in the case of the pausing of the cooking operation, even though it is inappropriate to increase a cooking time, the conventional microwave oven considers this cooling stage as a part of an entire cooking operation and accumulatively increases the cooking time.
Additionally, where a user manipulates a cancel key to cancel a corresponding cooking operation in progress, the control unit clears a counted cooking time as an initial value of 0, and then counts a new cooking time from the initial value of 0 according to newly set cooking conditions. Therefore, where the user repeatedly performs the setting of new cooking conditions and manipulates the cancel key, the electrical parts, including the high voltage transformer, are under substantially the same operating conditions as they would be under successive operations. However, since a cooking time is cleared due to the manipulation of the cancel key, an overheating prevention operation cannot be performed at a suitable time.
Accordingly, it is an object of the present invention to provide a microwave oven, and a method of controlling the same, which can suitably perform an overheating prevention operation by increasing/decreasing a cooking time according to cooking conditions.
Another object of the present invention is to provide a microwave oven, and method of controlling the same, which can improve a cooking performance by recovering an original output power level in response to cancellation of an overheating prevention operation.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided a microwave oven having a magnetron which outputs microwaves to cook food, an input unit which receives a target cooking time and an output power level, a high voltage transformer which supplies a high voltage to the magnetron, a power switch which selectively supplies/intercepts power to the high voltage transformer, and a control unit which increases a cooking time in response to a cooking mode which drives the magnetron, decreases the cooking time in response to a stop mode which stops the driving of the magnetron, and manages the output power level by controlling the power switch according to the increased or decreased cooking time.
In the microwave oven of the present invention, the input unit includes a pause key which temporarily stops the driving of the magnetron, and the control unit decreases the cooking time in response to a pause mode of the pause key which is recognized as the stop mode.
In the microwave oven of the present invention, the control unit compulsorily decreases the output power level in response to the cooking time being equal to or greater than a preset overheating prevention time, and recovers the output power level in response to elapse of a predetermined period of time after the output power level is decreased.
In the microwave oven of the present invention, the input unit includes a cancel key which stops the driving of the magnetron, and the control unit stores the cooking time in response to manipulation of the cancel key to stop the magnetron, and counts a new cooking time from the stored cooking time in response to the magnetron being driven according to new cooking conditions input through the input unit.
Additionally, the present invention provides a microwave oven having a heating unit which cooks food, a setting unit which obtains a target cooking time and an output power level, a driving unit which drives the heating unit, and a control unit which increases a cooking time in response to an operation of the heating unit, decreases the cooking time in response to the operation of the heating unit being stopped, and performs an overheating prevention operation by controlling the driving unit to decrease the output power level in response to the increased/decreased cooking time being equal to or greater than a preset time.
In the microwave oven of the present invention, the control unit recovers the output power level in response to elapse of a predetermined time after the output power level is decreased.
Furthermore, the present invention provides a method of controlling a microwave oven having a magnetron which outputs microwaves to cook food, the method comprising setting cooking conditions including a target cooking time and an output power level, performing a cooking operation according to the set cooking conditions, increasing or decreasing a cooking time according to whether the magnetron is driven, decreasing the output power level by a predetermined value in response to the cooking time being equal to or greater than a set time, and recovering the output power level in response to elapse of a predetermined time after the decreasing of the output power level.
The increasing or decreasing of the cooking time comprises increasing the cooking time in response to a cooking mode which drives the magnetron, and decreasing the cooking time in response to a stop mode which stops the driving of the magnetron.
The cooking time is decreased in response to a pause mode, which temporarily stops the cooking operation, and is recognized as the stop mode.
The method further comprises storing the cooking time in response to a cancel mode which cancels the cooking operation, and counting a new cooking time from the stored cooking time in response to performing another cooking operation according to newly set cooking conditions.